CN115249789A

CN115249789A - Method and apparatus for preparing battery electrodes

Info

Publication number: CN115249789A
Application number: CN202210457839.2A
Authority: CN
Inventors: 毛崚; A·K·萨奇德夫
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2021-04-28
Filing date: 2022-04-28
Publication date: 2022-10-28
Also published as: DE102022106386A1; US20220352496A1

Abstract

A battery electrode and a method of making the battery electrode are described. The battery electrode includes a lithium foil disposed between a first porous current collector and a second porous current collector. The first and second porous current collectors each define a plurality of interstitial spaces, and lithium foil is embedded in the interstitial spaces defined by the first porous current collector and the interstitial spaces defined by the second porous current collector, thereby performing a double-sided function.

Description

Method and apparatus for preparing battery electrodes

Introduction to

A lithium ion battery pack may include one or more lithium ion battery cells electrically connected in parallel or series depending on the needs of the system. Each battery cell includes one or more lithium ion electrode pairs encapsulated within a sealed soft envelope (sealed pouch envelope). Each electrode pair includes a negative electrode (anode), a positive electrode (cathode), and a separator that physically separates and electrically isolates the negative and positive electrodes. To facilitate lithium ion mobility, a lithium ion conducting electrolyte may be present within the separator. The electrolyte allows lithium ions to pass through the separator between the positive and negative electrodes to counter the flow of electrons that bypass the separator and move between the electrodes through an external circuit during charge and discharge cycles of the lithium ion battery cell. Depending on their chemistry, each lithium ion battery cell has a maximum or charging voltage (voltage at full charge) due to the electrochemical potential difference of the electrodes. For example, each lithium ion battery cell may have a charge voltage in the range of 3V to 5V and a nominal open circuit voltage in the range of 2.9V to 4.2V.

Each electrode pair is configured to electrochemically store and release electrical power. Each negative electrode has a current collector with a negative foil coupled to a negative terminal tab (negative terminal tab), and each positive electrode has a current collector with a positive foil coupled to a positive terminal tab. In each battery cell, the negative terminal tab is in electrical communication with the negative current collector, the negative current collector is in contact with the negative electrode of the electrode pair and exchanges electrons, the positive terminal tab is in electrical communication with the positive current collector, and the positive current collector is in contact with the positive electrode of the electrode pair and exchanges electrons. Lithium ion battery cells are capable of being discharged and recharged over multiple cycles.

It would be beneficial to provide improved electrode current collectors and to provide methods of manufacture related to the manufacture of improved current collectors.

SUMMARY

The present application relates to the following:

[1] a battery electrode, comprising:

a lithium foil disposed between the first and second porous current collectors;

wherein the first and second porous current collectors each define a respective plurality of interstitial spaces; and

wherein a lithium foil is inserted into the interstitial spaces defined by the first porous current collector and the interstitial spaces defined by the second porous current collector.

[2] A battery electrode as recited in the above [1 ]:

wherein the lithium foil is embedded in the interstitial spaces of the first portion of the first porous current collector;

wherein a lithium foil is embedded in the interstitial spaces of the first portion of the second porous current collector; and

wherein an electrical connection tab is disposed on the respective second portions of the first and second porous current collectors.

[3] A battery electrode as in [1] above, wherein the first and second porous current collectors are each comprised of metal wires (metallic strands) arranged to form a mesh defining the plurality of interstitial spaces.

[4] A battery electrode as recited in the above [3], wherein the metal wire is made of one of stainless steel or copper alloy.

[5] A battery electrode as in [4] above wherein the metal wire has a circular cross-section which has been flattened after weaving into a mesh.

[6] A battery electrode as in [1] above, wherein the first and second porous current collectors comprise respective metal sheets made of one of stainless steel or a copper alloy, and wherein the interstitial spaces comprise a plurality of perforations therein.

[7] A battery electrode as recited in [6] above, wherein the plurality of perforations are between 10 microns and 1000 microns in diameter.

[8] A battery electrode as recited in [1] above, further comprising a first separator disposed on a first side of the battery electrode and a second separator disposed on a second side of the battery electrode.

[9] A battery electrode as recited in [1] above, wherein the battery electrode comprises an anode.

[10] A method of making a battery electrode, the method comprising:

disposing a lithium foil between a first porous current collector and a second porous current collector, wherein the first porous current collector and the second porous current collector each define a plurality of interstitial spaces;

combining the lithium foil, the first porous current collector, and the second porous current collector such that the lithium foil is embedded in the plurality of interstitial spaces defined by the first porous current collector and the plurality of interstitial spaces defined by the second porous current collector;

bonding the lithium foil, the first porous current collector, and the second porous current collector; and

a passivated lithium foil, a first porous current collector, and a second porous current collector.

[11] The method as recited in the above [10], wherein the first porous current collector and the second porous current collector comprise first and second meshes composed of woven metal wires, respectively.

[12] The method as recited in [10] above, wherein the first and second porous current collectors comprise first and second sheets, respectively, of one of stainless steel or a copper alloy, and wherein the plurality of interstitial spaces comprise a plurality of perforations therein.

[13] The method as recited in [10] above, wherein combining the lithium foil, the first porous current collector, and the second porous current collector comprises compressing the lithium foil between the first porous current collector and the second porous current collector.

[14] The method as recited in [10] above, further comprising applying a coating to the first and second porous current collectors prior to disposing the lithium foil between the first and second porous current collectors.

[15] The method as recited in [10] above, further comprising warming the lithium foil, the first porous current collector, and the second porous current collector prior to compressing the lithium foil, the first porous current collector, and the second porous current collector, wherein warming comprises heating the lithium foil, the first porous current collector, and the second porous current collector to a temperature of at most 180 ℃.

[16] The method as recited in the above [10], wherein the joining the lithium foil, the first porous current collector, and the second porous current collector comprises heating the lithium foil, the first porous current collector, and the second porous current collector to a temperature of 180 ℃ to 200 ℃ in an atmosphere inert to lithium.

[17] The method as recited in [10] above, wherein passivating the lithium foil, the first porous current collector, and the second porous current collector comprises coating the lithium foil, the first porous current collector, and the second porous current collector with an antioxidant material.

[18] The method as recited in [10] above, further comprising disposing a first separator on a first side of a battery electrode and a second separator on a second side of the battery electrode; and compressing the first and second separators and the battery electrodes.

[19] A method of making a battery electrode, the method comprising:

compressing a first mesh of braided metal wires via a first pair of opposing rollers to form a first porous current collector;

compressing a first mesh of braided wires via a second pair of opposing rollers to form a second porous current collector;

[20] The method as recited in [19] above, wherein joining the lithium foil, the first porous current collector, and the second porous current collector comprises heating the lithium foil, the first porous current collector, and the second porous current collector to a temperature between 180 ℃ and 200 ℃ in an atmosphere inert to lithium.

A battery electrode and a method of making the battery electrode are described. The concepts described herein provide a lithium foil as the negative electrode sandwiched between two current collectors prepared as a metal mesh or perforated foil. The soft lithium in the lithium foil is squeezed into the interstices of the metal mesh and is thus accessible from either side. This enables a manufacturing process that includes a continuous roll-to-roll process to achieve double-sided electrolyte access (two-sided electrolyte access). The anode is made by a simple rolling step, wherein lithium is accessible from both sides in case the two meshes are in a sandwich configuration. The voids remaining on both surfaces of the mesh electrode provide volume or space for electrolyte and lithium ions to deposit during charging and minimize or prevent anode volume changes during charge/discharge cycles.

The metal mesh surface provides additional area and greatly reduces current density/Li ⁺ Ion flux, which reduces dendrite growth toThe fast charging capability is enhanced. A stable Solid Electrolyte Interface (SEI) may be formed at the interface between the mesh surface and the separator, which may be useful for improving durability. In addition, lower surface quality and higher lithium foil thickness can be used to reduce material costs.

One aspect of the present disclosure includes a battery electrode in the form of a lithium foil disposed between a first porous current collector and a second porous current collector. The first and second porous current collectors each define a plurality of interstitial spaces, and lithium foil is embedded in the interstitial spaces defined by the first porous current collector and the interstitial spaces defined by the second porous current collector, thereby performing a double-sided function.

Another aspect of the present disclosure includes a lithium foil embedded in the interstitial spaces of the first portion of the first porous current collector and the interstitial spaces of the first portion of the second porous current collector. An electrical connection tab is disposed on the second portion of the first and second porous current collectors.

Another aspect of the disclosure includes the first and second porous current collectors each being comprised of metal wires arranged to form a mesh defining the plurality of interstitial spaces.

Another aspect of the disclosure includes the metal wire being made of one of stainless steel or copper alloy.

Alternatively, the metal wire may be made of one of silver, nickel, zinc, tin, or an alloy thereof.

Another aspect of the disclosure includes the metal cords having a circular cross-section that has been flattened after weaving into a woven mesh.

Another aspect of the disclosure includes the first and second porous current collectors being metal sheets made of one of stainless steel or a copper alloy, wherein the interstitial spaces have a plurality of perforations therein.

Another aspect of the disclosure includes the plurality of perforations having a diameter between 10 microns and 1000 microns.

Another aspect of the present disclosure includes a first separator disposed on a first side of a battery electrode and a second separator disposed on a second side of the battery electrode.

Another aspect of the disclosure includes that the battery electrode is an anode.

Another aspect of the disclosure includes a method of making a battery electrode comprising disposing a lithium foil between a first porous current collector and a second porous current collector, wherein the first and second porous current collectors each define a plurality of interstitial spaces. Combining the lithium foil, the first porous current collector, and the second porous current collector such that the lithium foil is embedded in the plurality of interstitial spaces defined by the first porous current collector and the plurality of interstitial spaces defined by the second porous current collector. The lithium foil, the first porous current collector, and the second porous current collector are joined and passivated.

Another aspect of the present disclosure includes the first and second porous current collectors being first and second meshes comprised of braided metal wires.

Another aspect of the disclosure includes the first and second porous current collectors being first and second sheets made of one of stainless steel or a copper alloy, and wherein the plurality of interstitial spaces are a plurality of perforations therein.

Another aspect of the present disclosure includes combining a lithium foil, a first porous current collector, and a second porous current collector by compressing the lithium foil between the first porous current collector and the second porous current collector.

Another aspect of the present disclosure includes applying a coating to the first and second porous current collectors prior to disposing the lithium foil between the first and second porous current collectors.

Another aspect of the present disclosure includes warming the lithium foil, the first porous current collector, and the second porous current collector prior to compressing the lithium foil, the first porous current collector, and the second porous current collector, wherein the warming is performed by heating the lithium foil, the first porous current collector, and the second porous current collector to a temperature of at most 180 ℃.

Another aspect of the disclosure includes joining the lithium foil, the first porous current collector, and the second porous current collector by heating the lithium foil, the first porous current collector, and the second porous current collector to a temperature between 180 ℃ and 200 ℃ in an atmosphere inert to lithium.

Another aspect of the present disclosure includes passivating the lithium foil, the first porous current collector, and the second porous current collector by coating the lithium foil, the first porous current collector, and the second porous current collector with an antioxidant material.

Another aspect of the present disclosure includes disposing a first separator on a first side of a battery electrode and a second separator on a second side of the battery electrode; and compressing the first and second separators and the battery electrodes.

Another aspect of the present disclosure includes compressing a first mesh of woven metal wires via a first pair of opposing rollers to form a first porous current collector, and compressing the first mesh of woven metal wires via a second pair of opposing rollers to form a second porous current collector. The lithium foil is disposed between a first porous current collector and a second porous current collector, wherein the first and second porous current collectors each define a plurality of interstitial spaces. Combining the lithium foil, the first porous current collector, and the second porous current collector such that the lithium foil is embedded in the plurality of interstitial spaces defined by the first porous current collector and the plurality of interstitial spaces defined by the second porous current collector. The lithium foil, the first porous current collector, and the second porous current collector are joined and passivated.

The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings as defined in the appended claims when taken in connection with the accompanying drawings.

Brief Description of Drawings

One or more embodiments are now described, by way of example, with reference to the accompanying drawings, in which:

fig. 1 schematically shows an exploded isometric view of a battery cell including positive and negative battery tabs and electrode pairs in a stacked arrangement according to the present disclosure.

Fig. 2A and 2B schematically illustrate a top view and a cross-sectional end view, respectively, of one embodiment of an anode current collector according to the present disclosure.

Fig. 3 illustrates one embodiment of a method of making an electrode for a battery cell according to the present disclosure.

Fig. 4 illustrates another embodiment of a method of preparing an electrode of a battery cell according to the present disclosure.

Fig. 5 illustrates one embodiment of a portion of a method of making an electrode for a battery cell according to the present disclosure.

Fig. 6A-6D schematically illustrate a cross-sectional cutaway top view and a corresponding cross-sectional cutaway side view of a portion of an electrode of a battery cell according to the present disclosure.

The drawings are not necessarily to scale and present a somewhat simplified representation of various preferred features of the disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes. The details associated with these features depend in part on the particular intended application and use environment.

Detailed description of the invention

The components of the disclosed embodiments, as described and illustrated herein, may be arranged and designed in a wide variety of different configurations. The following detailed description is, therefore, not to be taken in a limiting sense, and is merely representative of possible embodiments thereof. In addition, while numerous specific details are set forth in the following description in order to provide a thorough understanding of the embodiments disclosed herein, some embodiments may be practiced without some of these details. Moreover, for the purpose of clarity, certain technical material that is understood in the related art has not been described in detail in order to avoid unnecessarily obscuring the present disclosure. Furthermore, the drawings are in simplified form and are not to precise scale. Directional terminology, such as top, bottom, left, right, upper, above, over, below, rear and front, may be used for convenience and clarity only to aid in describing the drawings. These and similar directional terms are illustrative and should not be construed to limit the scope of the disclosure. Further, the present disclosure as illustrated and described herein may be practiced in the absence of elements not specifically disclosed herein.

Referring to the drawings, wherein like reference numbers correspond to like or similar components throughout the several figures, fig. 1, 2A, and 2B schematically illustrate one embodiment of a prismatic lithium ion battery cell 10, including an anode 20, a cathode 30, and a separator 40, arranged in a stack and sealed in a flexible pouch (50) containing an electrolyte material 42. The first negative battery pack cell tab 12 and the second positive battery pack cell tab 14 extend from the pouch 50. The terms "anode" and "negative electrode" are used interchangeably. The terms "cathode" and "anode" are used interchangeably. A single pair of anode 20, cathode 30 and separator 40 is shown. It is to be appreciated that a plurality of pairs of anodes 20, cathodes 30, and separators 40 may be arranged and electrically connected in the pouch 50, depending on the particular application of the battery cell 10.

The anode 20 includes a first active material 22 disposed on an anode current collector 24, which is comprised of a first mesh 25 and a second mesh 26, wherein the first and

second meshes

25, 26 are porous sheets upon which the first active material 22 is consolidated, joined, and/or otherwise combined. The anode current collector 24 has a foil portion extending from the first active material 22 to form the first battery cell tab 12.

The cathode 30 includes a second active material 32 disposed on a cathode current collector 34, wherein the cathode current collector 34 has a foil portion 35 extending from the second active material 32 to form a second battery cell tab 14.

A separator 40 is disposed between the positive and

negative electrodes

30, 20 to physically and electrically separate the positive and

negative electrodes

30, 20 from each other. A lithium ion conducting electrolyte material 42 is contained within the separator 40 and exposed to each of the positive and

negative electrodes

30, 20 to allow lithium ions to move between the positive and

negative electrodes

30, 20. In addition, the negative electrode 20 contacts and exchanges electrons with the anode current collector 24, and the positive electrode 30 contacts and exchanges electrons with the cathode current collector 34.

The negative electrode 20 and the positive electrode 30 of each electrode pair are prepared as electrode materials capable of inserting and extracting lithium ions. The electrode materials of the positive and

negative electrodes

30, 20 are formulated to store intercalated lithium at different electrochemical potentials relative to a common reference electrode, e.g., lithium. In the configuration of the electrode pair 20, the negative electrode 20 stores intercalated lithium at a lower electrochemical potential (i.e., higher energy state) than the positive electrode 30, such that when the negative electrode 20 is lithiated, an electrochemical potential difference exists between the positive and

negative electrodes

30, 20. The electrochemical potential difference of each battery cell 10 results in a charging voltage in the range of 3V to 5V and a nominal open circuit voltage in the range of 2.9V to 4.2V. These properties of the negative and

positive electrodes

30, 20 allow lithium ions to be reversibly transferred between the positive and

negative electrodes

30, 20 either spontaneously (discharge phase) or by application of an external voltage (charge phase) during the operational cycle of the electrode pair 20. The thickness of each of the positive and

negative electrodes

30, 20 is between 30 μm and 150 μm.

Negative electrode 20 is a lithium host material such as graphite, silicon, or lithium titanate. The lithium host material may be mixed with a polymeric binder material to provide negative electrode 20 with structural integrity, and in one embodiment, with a conductive fine particle diluent. The lithium host material is preferably graphite and the polymeric binder material is preferably one or more of polyvinylidene fluoride (PVdF), ethylene Propylene Diene Monomer (EPDM) rubber, styrene Butadiene Rubber (SBR), carboxymethylcellulose (CMC), polyacrylic acid, or mixtures thereof. Graphite is typically used to prepare the negative electrode 20 because, in addition to being relatively inert, its layered structure exhibits favorable lithium intercalation and deintercalation characteristics, which help provide the desired energy density for the battery electrode pair 20. Various forms of graphite are commercially available that can be used to construct the negative electrode 20. The conductive diluent may be very fine particles of, for example, high surface area carbon black.

Positive electrode 30 is comprised of a lithium-based active material that stores intercalated lithium at a higher electrochemical potential (relative to a common reference electrode) than the lithium host material used to make negative electrode 20. The same polymeric binder materials (PVdF, EPDM, SBR, CMC, polyacrylic acid) and conductive fine particle diluents (high surface area carbon black) that may be used to construct negative electrode 20 may also be mixed with the lithium-based active material of positive electrode 30 for the same purpose. The lithium-based active material is preferably a layered lithium transition metal oxide, such as lithium cobalt oxide, a spinel lithium transition metal oxide, such as spinel lithium manganese oxide, a lithium polyanion, such as nickel-manganese-cobalt oxide, lithium iron phosphate or lithium fluorophosphate. Other suitable lithium-based active materials that may be used as lithium-based active materials include lithium nickel oxide, lithium aluminum manganese oxide, and lithium vanadium oxide, as examples of alternatives. Mixtures including one or more of these listed lithium-based active materials may also be used to prepare positive electrode 30.

The separator 40 is composed of one or more porous polymer layers, each of which may be composed of any of a wide variety of polymers. For simplicity, only one such polymer layer is shown here. Each of the one or more polymer layers may be a polyolefin. Some specific examples of polyolefins are Polyethylene (PE) (and variants such as HDPE, LDPE, LLDPE and UHMWPE), polypropylene (PP) or blends of PE and PP. The polymer layer serves to electrically and physically separate the negative and

positive electrodes

20, 30. The separator 40 may further penetrate the entire pores of the polymer layer with a liquid electrolyte. The liquid electrolyte that also wets both

electrodes

20, 30 preferably comprises a lithium salt dissolved in a non-aqueous solvent. The spacer 40 has a thickness that may be between 10 μm and 50 μm.

The above description of the anode 20, the cathode 30, the separator 40, and the electrolyte material 42 included within the separator 40 is intended as a non-limiting example. Many variations of the respective chemistries of these elements are possible in the context of the lithium ion battery cell 10 of the present disclosure. For example, the lithium host material of negative electrode 20 and the lithium-based active material of positive electrode 30 may be compositions different from those specific electrode materials listed above, particularly as electrode materials for continued research and development of lithium ion batteries. Additionally, the polymer layer and/or the electrolyte contained within the polymer layer of the separator 40 may also include other polymers and electrolytes in addition to those specifically enumerated above. In one variation, the separator 40 may be a solid polymer electrolyte including a polymer layer, such as polyethylene oxide (PEO), polypropylene oxide (PPO), polyacrylonitrile (PAN), or polyvinylidene fluoride (PVdF), with or swollen with a lithium salt solution. Electrode pair 20 reversibly exchanges lithium ions passing through separator 40 and electron flow around separator 40 during applicable discharge and charge cycles.

The anode and cathode

current collectors

24, 34 are thin metal plate-shaped elements that contact their respective first and second

active materials

22, 32 over a substantial interfacial surface area. The purpose of the anode and cathode

current collectors

24, 34 is to exchange free electrons with their respective first and second

active materials

22, 32 during discharge and charge.

The cathode current collector 34 is a flat plate made of aluminum or aluminum alloy, with a thickness equal to or close to 0.2 mm.

Fig. 2A and 2B schematically illustrate top and end views, respectively, of an anode 20 including a first active material 22 embedded and bonded to first and

second meshes

25 and 26 of a current collector 24. The first mesh 25 is arranged parallel to and above the second mesh 26. The first and

second mesh sheets

25, 26 are each comprised of a plurality of wires 27 that are woven, stitched, or otherwise arranged to form a mesh that defines a plurality of interstitial spaces 28 in the form of gaps, voids, or the like. The first active material 22 is embedded in the interstitial spaces 28 of the first and

second webs

25, 26. The surface of the first active material 22 is arranged so as not to extend beyond an outer plane 23, which is the height of the grid defined by the outer portions of the first and

second webs

25, 26 on either the first (top) surface 26A or the second (bottom) surface 26B.

The anode current collector 24 has a rectangular planar shape in one embodiment, and has a first top face 26A, a second bottom face 26B, a central portion 26C, and left and right longitudinal edges 26D. Alternatively, the anode current collector 24 may be circular or another shape as desired for a particular application. The wires 27 are made of stainless steel, copper, a copper alloy, nickel-plated copper, or another material, and are woven, stitched, or otherwise arranged to form one of the first and

second mesh sheets

25, 26. In one embodiment, the first and

second webs

25, 26 each have a thickness equal to or near 0.2 mm.

Alternatively, the first mesh sheet 25 and the second mesh sheet 26 are replaced by first and second solid sheets made of copper alloy, stainless steel, or the like and having a plurality of holes formed on the surfaces thereof.

The diameter of the metal line 27 is between 10 and 500 microns, and the plurality of interstitial spaces 28 defined by the metal line 27 have a maximum opening size that may be between one and ten times the diameter of the metal line 27. The wire 27 has a circular cross-section in one embodiment. Alternatively, the metal wire 27 has a rectangular cross section. Alternatively, the wire 27 has an elliptical cross-section. Alternatively, the wires 27 have a circular cross-section that has been flattened by a compressive force after weaving the first and

second mesh sheets

25, 26 as shown with reference to FIG. 4. In one embodiment, the wires 27 have a coating 29 that helps secure the first active material 22 embedded in the interstitial spaces 28 to the wires 27.

The coating 29 may be applied to the wires 27 in one embodiment prior to forming the first and

second webs

25, 26. Alternatively, the coating 29 may be applied to the first and

second webs

25, 26 during manufacture. In one embodiment, the coating 29 is one of tin, nickel or silver or an alloy thereof. Alternatively, the coating 29 may be a metal (e.g., ni, zn, sn, au, ag, cu) and their Li-intermetallic phase, a metal oxide (e.g., znO, cuO, al2O3, siO2, etc.), nitrogen-doped graphite, carbon nitrite (carbon nitride), and a polymer material such as PEO-based polymer, lanthanum Lithium Titanate (LLTO), lanthanum Lithium Zirconate (LLZO), lithium Aluminum Titanium Phosphate (LATP), lithium Phosphorous Sulfide (LPS), lithium phosphorous sulfide Chloride Iodide (LPSCl), etc.

The wettability of the first active material 22 on the first and

second webs

25, 26 can be adjusted by adjusting screen parameters, including screen spacing, thread diameter, thread cross-sectional shape, strain orientation, and mesh topology, i.e., woven or knitted mesh. The size of the interstitial spaces 28 affects the capillary force and the ability to embed and engage the applied lithium: if the gap is too large, molten lithium may sag or exfoliate; if too narrow, a strong wetting agent may be required to achieve adequate coverage of lithium onto the first and

second webs

25, 26.

Fig. 3 schematically illustrates one embodiment of an anode fabrication method (method) 300 for forming one embodiment of the anode 20 described with reference to fig. 1, 2A and 2B, wherein the anode 20 comprises a first active material 22 disposed on an anode current collector 24 comprised of first and

second mesh sheets

25, 26. The first active material 22 is embedded in the interstitial spaces 28 of the first and

second webs

25, 26 and bonded to the surfaces of the first and

second webs

25, 26. In one embodiment and as described herein, the first active material 22 is prepared as lithium foil 22A disposed on a spool.

Raw material is fed into the processing apparatus from a first reel 305 and a second reel 306 or from another feeding mechanism, wherein the raw material is in the form of a first web 25 and a second web 26, respectively. The first and

second webs

25, 26 are subjected to a cleaning step (step 310) to remove debris and other materials from their surfaces prior to entering an environmental chamber 311 which provides an atmosphere inert to lithium to prevent and avoid oxidation of the lithium. In one embodiment, the atmosphere in the environmental chamber 311 is oxygen-free. In one embodiment, the atmosphere in the ambient chamber 311 contains argon.

Raw material is also fed from the third reel 307 into the environmental chamber 311, wherein such raw material comprises the first active material 22 arranged as lithium foil 22A. The lithium foil 22A need not be continuous. The feeds from the first, second and

third reels

305, 306 and 307 are arranged in parallel.

After entering the ambient chamber 311, the first mesh 25, the second mesh 26, and the lithium foil 22A are subjected to warming (step 314), wherein warming includes heating to a temperature of at most 180 ℃.

After the warming step (step 314), the first and

second webs

25, 26 are coated with the coating 29 (step 316). This may include coating the first mesh 25 and the second mesh 26 with tin, nickel, or silver or alloys thereof prior to bonding with the first active material 22. The addition of the coating 29 is intended to remove oxidized metal from the surface, block air thereby preventing further oxidation, and promote fusion by improving surface wetting characteristics. The coating 29 also protects the metal surface from reoxidation during soldering and assists the soldering process by altering the surface tension of the molten solder. As mentioned above, the coating 29 consists of a binder and an activator, which is a chemical that promotes better wetting of the solder by removing oxides from the metal surface. The coating process (step 316) improves the wettability of the surfaces of the first web 25 and the second web 26 for the subsequently joined first active material 22.

The coating process (step 316) may be accomplished by dipping the first and

second webs

25, 26 in a bath comprising one of tin, nickel or silver or alloys thereof or by flash plating. Alternatively, the coating 29 may be applied to the first web 25 and the second web 26 and/or the individual strands thereof during the preparation of the first web 25 and the second web 26 prior to the method 300. Methods of applying the coating 29 to the first and

second webs

25, 26 include electrodeposition, physical vapor deposition, chemical vapor deposition, plasma spraying, and the like.

The coating layer 29 may be any one or combination of metals (Ni, zn, sn, au, ag, cu) and their Li-intermetallic phases, metal oxides (ZnO, cuO, al2O3, siO2, etc.), nitrogen-doped graphite, carbon nitrite, and polymeric materials such as PEO-based polymers, lanthanum Lithium Titanate (LLTO), lanthanum Lithium Zirconate (LLZO), lithium Aluminum Titanium Phosphate (LATP), lithium Phosphorus Sulfide (LPS), lithium Phosphorus sulfide Iodide (LPSCl), etc.

Lithium foil 22A is prepared in one embodiment as a thixotropic paste with stabilized lithium-containing microparticles, which are formed into flakes.

The lithium foil 22A is placed between the first mesh 25 and the second mesh 26 and consolidated by compressing the lithium foil 22A between them (step 322). This step embeds lithium foil 22A into the plurality of interstitial spaces 28 defined by first mesh sheet 25 and second mesh sheet 26, i.e., into the plurality of interstitial spaces 28 defined by the first and second porous current collectors.

The thickness of the lithium foil 22A is controlled while embedding the lithium foil 22A to suspend the lithium foil 22A in the grid of the first and

second mesh sheets

25, 26 at or below the grid height defined by the outer plane 23 as shown and described with reference to fig. 2B.

Referring again to fig. 3, the applied and intercalated lithium is bonded, i.e., fused or bonded, to the first and

second mesh sheets

25, 26 of the anode current collector 24 by applying heat to melt the lithium powder contained in the lithium foil 22A so that it fuses, adheres or otherwise bonds with the first and

second mesh sheets

25, 26 in the interstitial spaces 28 (step 326). Heating to bond the lithium includes heating the first mesh 25 and the second mesh 26 in an inert environment to a temperature in a temperature range between 180 ℃ and 200 ℃. In one embodiment, the heating step lasts 30 minutes or less. Heating may be achieved by a heat furnace, an infrared heat source, a resistive heating device, an inductive heating device, or another heat generating device.

After the heating step (step 326), the anode 20 is passivated (step 328), which includes applying an antioxidant material, such as a polymer substance, to the outer surface of the anode 20 to prevent oxidation of the lithium. The passivation step (step 328) includes, in one embodiment, applying the antioxidant material in the form of a spray delivered by a sprayer (not shown). The temperature of the spray from the atomizer may be controlled to controllably cool the first mesh 25 and the second mesh 26 to manage the lithium and physical shrinkage of the first mesh 25 and the second mesh 26, thereby minimizing or preventing deformation of the first mesh 25 and the second mesh 26 and minimizing or preventing lithium from separating from the first mesh 25 and the second mesh 26. The resulting workpiece is one embodiment of the anode 20 described with reference to fig. 1, 2A, and 2B.

Fig. 4 schematically illustrates another embodiment of an anode fabrication process (method) 300' for forming one embodiment of the anode 20 described with reference to fig. 1, 2A, and 2B. The anode preparation method (method) 300' is similar to the anode preparation method (method) 300 described with reference to fig. 3. In this embodiment, the raw material is fed into the processing apparatus from a first reel 305 'and a second reel 306' or from another feeding mechanism, wherein the raw material is in the form of a first web 25 and a second web 26, respectively. In this embodiment, the first and

second mesh sheets

25, 26 are subjected to a cleaning step (step 310) to remove debris and other materials from their surfaces and a compression step (step 312) prior to entering the environmental chamber 311 which provides an atmosphere inert to lithium. In the compression step (step 312), the first and

second webs

25, 26 pass between two rolls to flatten the respective sheets. Thereafter, the method 300' proceeds in a manner similar to the method 300.

Fig. 5 schematically illustrates a method 300 with the addition of a subsequent method step 330 to embed a separator 40 (as shown) on both sides of the anode 20 to form a separator-encapsulated anode 45, wherein there is a double-sided electrolyte access to lithium in the anode 45. The lithium foil need not be continuous to avoid having lithium at the folds. Alternatively, an added subsequent method step 330 embeds the separator 40 on a single side of the anode 20. The other steps of the method 300 remain unchanged.

In one embodiment, the subsequent method step 330 of embedding the separator 40 on both sides of the anode 20 is performed in the environmental chamber 311 (as shown). Alternatively, the subsequent method step 330 of embedding the separator 40 on both sides of the anode 20 is performed outside the environmental chamber 311.

Fig. 6A-6D schematically illustrate a cross-sectional cutaway top view and a corresponding cross-sectional cutaway side view of a portion of one embodiment of an electrode of a battery cell as described herein.

Fig. 6A shows a consolidated electrode in which lithium is intercalated into the plurality of interstitial spaces defined by the first mesh sheet and the plurality of interstitial spaces defined by the first mesh sheet.

Fig. 6B shows a Solid Electrolyte Interface (SEI) layer 21 formed on the mesh surface and the lithium surface once the electrolyte fills the voids formed in the interstitial spaces of the electrode mesh.

Fig. 6C shows that lithium ions from the electrode are deposited in the interstitial spaces 28 on the surface of the mesh and lithium. Interstitial spaces 28 provide space for lithium dendrite growth.

Fig. 6D shows that a stable SEI layer 21 is formed on the mesh electrode at the interface between the mesh surface and the separator after a plurality of discharge/charge cycles, which improves the cycle performance of the battery 10, and thus can improve the service life of the battery 10.

The detailed description and drawings are supportive and descriptive of the present teachings, but the scope of the present teachings is defined solely by the claims. While some of the best modes and other embodiments for carrying out the present teachings have been described in detail, there are various alternative designs and embodiments for practicing the present teachings as defined in the appended claims.

Claims

1. A battery electrode, comprising:

a lithium foil disposed between the first porous current collector and the second porous current collector;

wherein a lithium foil is embedded in the interstitial spaces defined by the first porous current collector and the interstitial spaces defined by the second porous current collector.

2. The battery electrode of claim 1:

3. The battery electrode of claim 1, wherein the first porous current collector and the second porous current collector are each comprised of metal wires arranged to form a mesh defining the plurality of interstitial spaces.

4. The battery electrode of claim 3, wherein said metal wire is made of one of stainless steel or copper alloy.

5. The battery electrode of claim 4, wherein the metal wires have a circular cross-section that has been flattened after weaving into a mesh.

6. The battery electrode of claim 1, wherein the first and second porous current collectors comprise respective metal sheets made of one of stainless steel or a copper alloy, and wherein the interstitial spaces comprise a plurality of perforations therein.

7. The battery electrode of claim 6, wherein the plurality of perforations are between 10 microns and 1000 microns in diameter.

8. The battery electrode of claim 1, further comprising a first separator disposed on a first side of the battery electrode and a second separator disposed on a second side of the battery electrode.

9. The battery electrode of claim 1, wherein the battery electrode comprises an anode.

10. A method of making a battery electrode, the method comprising: